The Z71 packages on the Chevrolet Silverado and GMC Sierra do not include a locking rear differential. You can order a locking rear diff on a Z71-equipped pickup, but the contents of the Z71 package are primarily suspension and appearance add-ons.
On most Silverado and Sierra configurations, a locking differential is available as a stand-alone option for $325. It’s also included in a trailering package that equips the truck with a hitch and associated wiring and equipment; package pricing varies depending on transmission. Silverados in LTZ trim levels come with a locking differential standard.
A locking rear differential will greatly improve traction compared to a limited-slip or open differential. It locks both wheels together to spin at the same speed for maximum traction. On the Silverado and Sierra, this can happen at speeds slower than 20 mph, and it does it automatically.
The Z71 package includes shock absorbers, wheels and tires better suited for off-road use. The front sway bar has been upgraded; a skid-plate package and Z71 decals are also added.
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